_io.IncrementalNewlineDecoder doesn't inherit codecs.IncrementalDecoder

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-10-07.14:26:41.466>
labels = ['3.7', '3.8', 'type-bug', 'library', 'expert-IO']
title = "_io.IncrementalNewlineDecoder doesn't inherit codecs.IncrementalDecoder"
updated_at = <Date 2019-10-08.18:46:56.963>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2019-10-08.18:46:56.963>
actor = 'corona10'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)', 'IO']
creation = <Date 2017-10-07.14:26:41.466>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 31722
keywords = ['patch']
message_count = 3.0
messages = ['303879', '303880', '328293']
nosy_count = 5.0
nosy_names = ['benjamin.peterson', 'stutzbach', 'serhiy.storchaka', 'xiang.zhang', 'corona10']
pr_nums = ['16664']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue31722'
versions = ['Python 2.7', 'Python 3.6', 'Python 3.7', 'Python 3.8']